In general, brushes for a motor are mounted so that they come into elastically sliding contact with a sliding surface of a commutator connected to an armature shaft. As a result, when the commutator is absent, the brushes project inwardly beyond the sliding surface of the absent commutator. To overcome this problem, a method is used where each brush is temporarily held against a spring at a position spaced apart from a commutator during assembly of an armature and then the temporarily held brush is released. In this case, however, the task of holding and releasing each brush is time-consuming and troublesome and presents the possibility of sometimes forgetting to perform this task.
Consequently, as disclosed in Japanese Utility Model Unexamined Publication No. Sho 58-115862 and Japanese Utility Model Unexamined Publication No. Sho 58-166262, a method is disclosed in which a brush unit has brushes preset in a brush holder. An opening is formed in a holder stay unit, in which the brush unit is to be mounted and then the brush unit is inserted in the opening of the holder stay unit after an armature has been preassembled. In the method in Publication No. Sho 58-115862, however, a brush unit must be formed for each brush and each brush unit having a brush must be engaged and assembled. Accordingly, since as many brush units are needed as there are brushes, the number of parts is increased and production output is lowered. Further, since the brush is biased to significantly project from the brush unit by a spring assembled in the brush unit, a problem arises in that the brush is in contact with other parts and is liable to be damaged by the other parts before the brush unit is completely assembled to the holder stay unit.
On the other hand, in Publication No. Sho 58-166262, since a pair of brushes are assembled in a brush unit, there is an advantage that the number of brush units can be reduced to half those in Publication No. Sho 58-115862. In this case, however, since a brush accommodation unit is not used, each brush is biased and held from significantly projecting by the use of a leaf spring fixed to a brush holder. Thus, the brush is not stably held by a brush accommodation unit. Further, a guide receiving portion is formed at the extreme end of the leaf spring to guide the brushes into sliding contact with a commutator in such a manner that the guide receiving portion is in contact with the periphery of the commutator and to increase the distance between the confronting brushes. Consequently, the possibility of the surface of the commutator being scratched by the guide receiving unit arises.